Notes:Dr. Mario (NES)

This page contains notes for the game Dr. Mario (NES).

Controller Polling Routines

The controller polling routines appear to originate from the FDS BIOS, including the zeropage variables ($F1-$F8) and routines which went unused in the final game.

Below is a table of these routines from the final game, mapped to their equivalents from the FDS BIOS:

Rev 1 ROM Address	FDS BIOS Address	Description
$B7AD	$E9EB	Polls the standard controllers and the expansion port. The expansion port inputs are placed into temporary variables (zeropage $00-$01) which will be overwritten unless they are stored/used elsewhere.
$B7CF	$EA0D	Combines the inputs from the standard controllers and the expansion port.
$B7DC	$EA1A	Polls the standard controllers and processes button transitions.
$B7E1	$EA1F	Polls the standard controllers and the expansion port, then processes button transitions. The final game modifies this routine to store the bitwise AND of two consecutive polls, using zeropage variables $48-$49 to temporarily save the poll results.
$B801	$EA25	Entry point to process button transitions from released->pressed.
$B812	$EA36	Polls the standard controllers in a loop until two consecutive reads match, then processes button transitions.
$B828	$EA4C	Polls the standard controllers and expansion port in a loop until two consecutive reads match, then processes button transitions.
$B844	$EA68	Polls the standard controllers and expansion port, places the expansion port inputs into separate variables, and then processes button transitions. This creates four player inputs.